The invention relates to a mask for depositing and distributing one or more reagents on an analytical support, in particular a support for electrophoresis, for example agarose gel.
The invention is suitable for use, for example, in the field of detecting and characterizing constituents present in a biological sample, in particular a biological liquid such as serum, urine or cerebrospinal fluid. In particular, such detection can be carried out following separation of said constituents from a biological sample, for example, using electrophoresis. Detection can then be carried out in particular using known immunofixation techniques, which require bringing reagents into contact with the constituents separated from the sample and incubating them to produce an immunological recognition reaction of the constituents separated from the biological sample with the reagents in predetermined zones of an analytical support.
The invention is advantageously used for routine analyses, particularly of the type carried out in the context of clinical analyses.
The invention also relates to a mask intended for depositing and distributing one or more reagents on an analytical support, associated in a device with positioning means that allow the mask to be positioned with respect to the analytical support, in the proximity of said support, when the mask is used to deposit and distribute the reagents.
These positioning means can also be associated with guide means or can comprise guide means for displacing the mask when it is positioned in the proximity of the analytical support, to allow the reagents to be distributed onto delimited zones of the support, including zones designated for incubation of the reagents with the constituents of the sample.
The device of the invention allows reagents to be deposited or distributed manually. It can also be arranged for automated deposition of these reagents and optionally for automated distribution.
In some embodiments of the invention, the step for loading the reagents into the mask can also be carried out manually or in an automated manner. Advantageously, the mask of the invention is more easily loaded than available prior art masks.
In a further aspect, the invention provides a method for depositing and distributing reagents on an analytical support.
In one particular implementation of the invention, the method is used to deposit and distribute reagents intended to carry out immunofixation to detect and possibly quantify specific constituents contained in a biological sample, said constituents having already been separated by electrophoresis on a support such as agarose gel.
The invention also concerns an immunofixation method employing said mask.
In a further aspect, the invention provides a kit comprising a mask in accordance with the invention.
A kit in accordance with the invention is advantageously adapted to carry out an immunofixation method using the mask of the invention.
The invention also concerns means for positioning and guiding the mask.
It should be remembered that immunofixation, which can analyse biological samples with a view to typing the paraproteins they contain, is a widely practised routine analysis carried out in clinical analysis laboratories in particular.
That technique, which combines electrophoresis with the formation of precipitates on the electrophoresis gel, has been known for a long time. The technique has in particular been described by Alper C A and Johnson A M Vox. Sang. 17: 445 (1969), Cawley L P et al., Clin. Chem. 22: 1262 (1976), Ritchie R F and Smith R Clin. Chem. 22: 497, 1735, 1982 (1976). It allows the identification of anomalies in different biological samples, in particular in biological liquids, for example serum, urine or cerebrospinal fluid.
The technique principally comprises the following steps:
1) separating protein constituents from the test serum or liquid by electrophoresis on a support such as a gel, for example agarose gel;
2) an immunological reaction with specific antibodies for the separated proteins;
3) revealing the immunological complexes formed.
The conditions for carrying out these steps have been described in the prior art.
The devices used also comprise the possibility of producing a reference lane (track) on the same electrophoresis support, in particular on the same gel, obtained by fixing all of the separated proteins present on the sample using a protein fixative including, for example, a polyvalent antiserum.
New semi-automatic techniques for applying the biological samples to be analyzed, for migration under controlled temperature and for depositing the reagents (including, for example, the antiserums and fixatives) allow immunofixation profiles to be miniaturized while keeping the sensitivities and resolutions satisfactory. Miniaturization allows a larger number of samples to be analyzed on the same electrophoresis support, in particular on the same gel.
Thus, in a few years we have advanced from carrying out one to carrying out nine immunofixations on a single 8×10 cm electrophoresis gel (using, for example, an immunofixation kit sold by SEBIA under the trademark Hydragel 9 IF). This saves time as regards the analysis and reduces reagent consumption, resulting in a reduction in analytical costs.
To deposit the reagents with a view to carrying out immunofixation under such conditions, European patent EP-B1-0 526 271, for example, describes a mask or device for distributing reagents, generally specific antiserums and a fixative, that can overcome some of the problems posed by prior art devices or masks and that is safer and easier to use. Thus, to carry out 9 immunofixations, for example, on the same electrophoresis gel in three rows of three samples using the mask described in EP-B1-0 0 526 271, for each sample, 6 reagents have to be pipetted out (fixative, anti-IgG antiserum, anti-IgA antiserum, anti-IgM antiserum, anti-k antiserum and anti-λ antiserum), i.e., a total of 54 pipetting operations.
These manual pipetting operations can prove to be long and difficult even if repetitive dosing pipettes are used.
The primary aim of the present invention is to improve the conditions for depositing and distributing reagents on an analytical support using masks, by proposing a mask that can reduce the number of reagent pipetting operations and which can reduce the quantity of reagents used. The means proposed in the context of the invention can be used in any analytical technique requiring controlled deposition of reagents on an analytical support. In this respect, the following techniques can be mentioned: immunofixation following electrophoretic separation; or distribution onto a specific substrate for enzymatic developing, for example for assaying lactodehydrogenase (LDH) or creatine kinase (CK).